Electrical regulation



' P 2, 1940- I L. w. THOMPSON 2,196,04

ELECTRICAL REGULATION Filed Aug. 10, 1937 on no ,8

6 o 8 TH! PI'IASE RECT/F/ER Inventor: Louis W. Thompson His Attorney.

Patented Apr. 2, 1940 ATENT OFFICE to General Electric Comp ny. a corporation oi New York Application 1mm: 10, 1937, Serial No. 158,303

achin (Cl. ran-22 4 M! invention; relates to electrical regulators show therein by way of example a main alternatand-.regulatingsystems and it has for its :prining current machine i connectedto a power circipal1ohject:the.stabilization of the voltage of cult 2. Machine I may for example be a threerheostatically controlled self-excited dynamophase synchronous generator. This machine is 5 electric-machines. especially-i shunt connected provided with a field winding 3 energized by a 5 fireet ourrent exclters q 1 direct current self-excited generator 4 having a Assumingother: conditionsoi operation conshunt field winding 4' in series with which is stant i; every dynamo-electric generator has a connected an adjustable regulating rheostat 5.

given characteristic curve oi armature voltage Rheostat 5 may be manually operated if desired compared withv field current. This curve correbut as shown it is automatically operated in resbbnds tothe magnetization curve of the magsponse to the voltage of the maincircuit 2 by netic circuit of the generator. Shunt-field curmeans of a reversible servomotor 6 whose direcrent,-however, is dependent on the resistance of tionoi' operation is controlled by any suitable it circuit a w ll upon th generator voltage, voltage sensitive controller, such as a contact- Ordinary stable operation of shunt machines is making voltmeter I. Both the motor 6 and the 16 a't-a point on the characteristic curve where the meter 1 are connected to respond to the voltage ration! generator voltage toigenerator shunt field of all of the phases of the circuit 2 by means of a c r t gqualsjhe resistance 1' th -g n r t rsuitablc three-phase rectifier 8' energized by the h t-fl Idd -Mt H i, th vo]tgge.charline to line voltages of the circuit 2 through so acteristic. .o1 most generators is-such that at the n al transformers 9. I on lower values, 0! voltage itis almost a straight In orderto stabilize the voltage of exciter 4, line passing through theorigin of coordinates so I connect the armature of an auxiliary direct that over a;considerable-range'ot terminal voltcurrent dynamo in across the rheostat 5. This agesand -field,current the ratio of voltage to auxiliary machine has-a field winding I l which curl-ent i s substantially constant; This means is connected to respond to the voltageof exciter as that when the generator-shunt field circuit has a as by con c in i di ly a r ss the terresistance having'this constant ratio; the voltage m ls t reof. The ma hin w h y a of the generator is unstable and it may have any e rmed a counter E. M. F. generator or motor value over. this constant ratio range, 3 is free to rotate at any speed and is not mechan- In accordance with my invention..I stabilize lcal y connect d to the main generator I or to 30 r the voltage oiashunt-exclted generator by means the exciter 4. In order to provide a forcing of an auxiliary dynamo-electric machine for inaction by t e regulating system as a whole and gel-ting. t' u u v r b potential in th also in order to provide an anti-hunting eiiect, shuntileldcircuit. This potential acts to oppose the armature of machine It is given an abnorany ehange in field current at anyparticular mally high moment of inertia by any suitable 35 sotting oi iield-resistanceand, therefore, permits means such as providing it with a fly-wheel i2. stableeoperation oi the generator at values of h Will be pl ined f rther on. field circuit resistance which, otherwise i would Although machine 4 is reierredto as an excause voltage instability.- V 4 citer it is of course also a shunt-connected direct- 40 An object of my inventionis to provide a new current generator which is suitable for general 40 and improved generator voltage. regulating pu p e Operation circuit. g g V I g g The way the voltage of generator 4 is stabilized Another. object of myinventionu to provide by means of the counter E. M. F. machine It is a new and improved arrangement for stabilizing. as follows. Assume machines i and 4 are being the voltage of shunt-excited generators. driven at constant speed by any suitable means 45 Another object oi myinvention is to provide (not shown). With the rheostat 5 set in any a newand improved automatiodynamo-electric given position. such as the illustrated position. machine regulating system. g v the voltage of' the generator 4 will be determined My invention will be better understood from primarily by the setting of the rheostat. The

60 the following description taken in connection counter E. M. F. machineiil will be energized withuthe accompanying drawing and its scope -by a voltage which equals the voltage drop will be pointed outv in 'the appended claims, through the effective portion of the regulating Referring now to the single figure oi the acrheostat 5 and as the machine I0 is free to rotate companying drawing, which illustrates diagram- .at any speed it will inherently reach a steady 5 matically an embodiment of my invention, I state condition at which it will operate as a in the field winding 1! of the counter E. M. F.

machine In which, due to its characteristics tends.

momentarily to keep rotating at substantially the same speed. Consequently the counter E. M. 1-". generated in the armature H) of the auxiliary machine increases and this opposes a change in current in the field winding 4. Aftera time, machine i0 reaches a new steady state condition of operation corresponding to the new, voltage drop across the regulating rheostat and to the higher voltage of the generator 4. Similarly if the rheostat arm is moved to the left so as to increase the effective resistance of the rheostat the current in the field winding of the generator 4 decreases thereby decreasing the generator voltage. However a decrease in voltage across the terminals of the generator 4 decreases the current in the field winding ll of the auxiliary machine thereby decreasing the counter E. M. F. generated by this machine and opposing the decrease in current in the field winding of the main generator 4. However, this action will soon settle down to a steady state value at the new value of voltage of generator 4. It will thus seem that counter E. M. F. machine I0 is an electromechanical damping device for retarding change in exciter voltage.

If now rheostat 5 is moved to cut in still more resistance until the zone of ordinary unstable voltage operation is reached voltage instability.

will be prevented because whenever the voltage of generator 4 starts to rise, the counter electromotive force of the machine 14 also increases due to the increase in the energization of its field winding H thereby bucking down an increased field current in the generator 4 and preventing further rise in voltage. Similarly, if the voltage of generator 4 tends to fall the field ID of the auxiliary machine is weakened thereby weakening the counter E. M. F. developed by this machine and in turn preventing the field current of the generator 4 from falling in response to the decrease in terminal voltage of the machine. As a result there may be relatively slight oscillations in the magnitude of the counter E. M. F. generated in the machine II! when the rheostat 5 is holding a value of resistance normally tending to cause instability. However the voltage of generator 4 will be substantially constant and there will be adefinite value of voltage for each different position of the rheostat 4.

In the automatic operation of the regulating system the contact-making voltmeter I will be balanced in its illustrated mid-position it normal voltage exists on circuit 2. If the voltage falls the moving contact of the voltmeter engages its uppermost fixed contact thereby completing an energizing circuit for the motor 6 and causing the rheostat to decrease its resistance and thus raise the exciter voltage and consequently the voltage of the main alternator I. Similarly if the voltage of the main circuit rises the contact-making voltmeter closes its other set of contacts thereby reversing the motor 6 and causing the rheostst to increase its resistance thereby to decrease the excitation and voltage 0! the dynamo-electric machines 4 and I.

Sometimes regulating rheoststs have maximum values of resistance which are so high as to prevent a self-excited generator from building up voltage However, with my arrangement this cannot happen because the armature resktance of the auxiliary machine II is always very low so that when the machine 4 is at rest the rheostat is substantially short circuited no matter what its resistance value is. Consequently, current will always build up in the field 4' due to residual magnetism in the main machine and as soon as the counter E. M. F. machine corms up 18 to speed its counter E. M. P. will hold the field current substantially constant at a value determined by the setting of the rheostat.

"In some regulating systems, such as the one illustrated in the drawing, the motor for operating the rheostst is energized from the main power circuit. If now there should be a failure of power to themotor 6, as by a break in the connections or an opening of a circuit breaker at a time when the resistance 0! the rheostst 5 is a maximum an ordinary regulating system of this type might not build up again when the system is again started. However, as previously explained the presence of my counter E. M. 1''.

machine Ill always insures that the voltage or the exciter will build up.

The presence of the flywheel It causes a dcsirable field forcing and anti-hunting action as follows: The flywheel retards the acceleration of the counter E. M. F. machine ll thus allowing the exciter voltage to go slightly beyond the point to which it would otherwise go. As the motor comes up to speed the cxciter voltage backs down which gives an inherent anti-hunting oction. In other words, the counter 12. M. l". of

the machine II is proportional to the product of its speed and field current and the flywheel retards the rate of change 0! its speed. Therefore, it takes longer to settle down to a steady state value after each change in setting of the rheostat and this permits a forcing or over-shooting of the field excitation of the generator 4 with a later backing oil and settling down of this voltage to its normal steady state value.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications can be made without departing from my invention and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a generator having a direct current shunt field winding, a rheostat in series with said field winding, said rheostat being arranged to operate continuously at adjustable resistance values high enough normally to cause voltage instability of said generator, and means for inserting a variable potential in circuit with said field winding of such magnitude and direction as to oppose current changes in said shunt field winding circuit thereby to stabilize the voltage of said generator at any setting of said rheostat, said means being automatically responsive to changes in voltage of said generator.

2. In combination, a direct current generator having a shunt field winding, 8. rheostat in series with said field winding, said rheostat being arranged to operate continuously at adjustable resistance values high enough normally tocause voltage instability of said generator, and means for inserting a variable counter electromotlve force in circuit with said field winding of such magnitude asto oppose current changes in said field winding circuit thereby to stabilize the voltage of said generator at any setting of said rheostat, said means being automatically responsive to changes in voltage oi said generator.

3. In combination, a self-excited direct current generator adapted for constant speed operation, a shunt field winding for said generator, a rheostat in series with said field winding, a direct current dynamo-electric machine having an armature which is connected in parallel with said rheostat, said armature being free to rotate independently of said generator, and a field winding for said dynamo-electric machine connected to be energized in accordance with the voltage of said generator.

4. In combination, a self-excited direct current exciter adapted for constant speed operation, a shunt field winding for said exciter, a rheostat in series with said field winding, a counter electromotive force machine having an armature which is connected in parallel with said rheostat, said armature being free to rotate independently of said exciter, and a field winding for said counter electromotive force machine connected across the terminals oi said exciter.

5. In a regulator system for a main generator,

4' provided with means ior giving it an abnormally highmomentoiinertigandmeansresponsiveto the voltage of said generator for adjusting said rheostat.

6. In combination, a main dynamo electric machine, a field winding on said machine connected to be energized in accordance with the voltage of said machine, a rheostat connected to control the voltage of said machine by controlling the current in said field winding, and an auxiliary dynamo-electric machine having a relatively low resistance armature which is connected directly across said rheostat for insuring self-excited voltage build-up 01 said main machine at any setting of said rheostat.

7. In combination, a self-excited dynamo-electric machine, means for controlling the excitation of said machine so as to vary the voltage thereof, said means having a plurality of settings which cause voltage instability of said machine, and electro-mechanical damping means connected to produce automatically in response to changes in the excitation of said machine counter effects foropposing said changes thereby to stabilize the voltage of said machine at any setting of said controlling means.

8. In combination, a self-excited constantspeed direct-current exciter for a main dynamoelectric machine, a shunt connected field winding for said exciter, a regulating rheostat connected in series with said winding, said rheostat having resistance values at the high resistance end of its range which are so high as normally to cause voltage instability of said exciter when it is operating with the rheostat adjusted within said high resistance range and to prevent selfexcited voltage build-up of said exciter when it is started with the rheostat adjusted within said high resistance range, means for stabilizing the exciter voltage and permitting voltage build-up thereof when the rheostat is adjusted within said high resistance range comprising a freely-running direct-current dynamo-electric machine armature connected directly across said rheostat, a flywheel mounted on the shaft of said armature, and a field winding for said armature connected directly across the terminals said exciter.

IDIJIB W. THOMPSON. 

